Specialised ‘Saildrones’ could open up new areas of marine science

A partnership with CSIRO and Saildrone has developed a fleet of wind and solar-powered autonomous vehicles that have been deployed to capture ocean data.

The Saildrones will be deployed at sea for up to 12 months. Their systems will be remotely controlled, with the data accessible from anywhere in the world in real time.

Each Saildrone has been equipped with a series of oceanographic sensors that will capture and send back data to a science team, with the ability to change data settings, turn sensors on or off, or change the sampling rate to allow the team to capture more data over a longer period of time.

Some of the sensors are off-the-shelf, having undergone some high-level calibration and analysis carried out by CSIRO to understand their behaviour when they’re operating in unmanned conditions.

But Andreas Marouchos, Research Group Leader, Engineering and Technology Program at CSIRO, said a lot of the sensors are new and experimental, and CSIRO worked with research partners to develop some of the methods over a number of years.

One partnership is with NOAA-PMEL in the United States, which developed a high-precision, high-accuracy carbon sensor to measure the concentration and uptake of carbon in the water.

This included the challenge of taking technology that has been used on research ships and miniaturising it, making it more robust and reducing its power consumption so it can operate sustainably and unattended.

Measuring carbon on a large ship means having access to significant infrastructure including large pumps with large flow rates and a large supply of reference gasses used to control and calibrate the detection process.

But on a small vehicle like the Saildrone, running a pump or switching a valve requires power, which can be a challenge when there is a limited power budget to pump samples through the system and limited space to carry reference gases.

“So we had to come up with ingenious ways to use less reference gas, less water and have the system running for as short a period of time as possible, but still allow us to collect the data,” he says.To make the most of the limited power and computing resources, the team applied data processing techniques to make intelligent decisions about when to turn the system on and what is sampled. Another challenge was getting the sensors to operate reliably without intervention for months on end while maintaining accuracy and precision.

“When operating in the lab, sensor platforms are static – they don’t move – and they

don’t see the same sort of dynamic forces that you would expect from a surface vehicle. So making sure that those sensors were robust enough to withstand those conditions was really important,” Marouchos says.

Testing the waters

The team conducted a series of validation trials in San Francisco Bay late last year.

The systems were then shipped to Australia and tested again to ensure they had survived the shipping process.

The team spent about two weeks carrying out detailed calibration of the systems to detect if there were any changes from San Francisco Bay waters to Australian waters, as both locations have different quality parameters.

The CSIRO Oceans and Atmosphere team with a Saildrone.

“When we’re looking at bioacoustics, for example, there are different critters in the water, so we need to calibrate both the optical systems and the bioacoustics systems for the local water parameters,” Marouchos says.

Following this testing, the Saildrones were deployed from Hobart before Easter. One of them is currently heading down to the Southern Ocean for the winter, with the team keen to observe its performance in the aggressive sea states and weather conditions of those waters.

The other two Saildrones will be focused primarily on regional Australian waters, and likely to stay around the Tasmanian region and the Great Australian Bight to aid of a variety of science including in support of carbon capture and storage projects.

The vast amount of data that the Saildrones can collect could also lead to other new applications and potentially even prompt the development of bespoke sensors and sensor technologies geared toward unmanned surface vehicles and other areas of marine autonomy.

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